COLUMN: Weather Wise with Gordon Currie

There was heavy snow in March as we awaited the late spring. (Picture ' Pete Colman)

There was heavy snow in March as we awaited the late spring. (Picture ' Pete Colman)

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Gordon takes a look at the sunless days of March, and gives prospects for the week ahead.

‘Today, I saw the catkins blow,

Altho’ the hills are white

With snow . . . .

They come to greet the lurking

Spring,

As messengers from Winter’s

King.

And thus they wave while

Winter reigns,

While his cold grip still holds

The plains.’

This delightful dedication inspired by Dorothy Una Ratcliffe was originally written for the month of February, though in actual fact the message appropriately reflects the final days of March 2013.

On the penultimate day of the month, I came across a captivating scene of one tree smothered in yellow hazel catkins caught in a shaft of sunlight against a contrasting background of snow-capped Cleveland Hills which created a realistic pictorial signature to the weather of the month.

Further westwards in Upper Wensleydale, the sculpture of shrinking snow drifts caught the traveller’s eye on Easter Sunday. Strikingly artistic to the painter perhaps, but ominously fatalistic to the recent experiences of the hill sheep farmers for whom the spectre of the devastating lambing storms of March 1947 re-appeared once again.

I place these impressions on record, alongside the meteorological events of last month which highlighted the unique wintry character of March past and present.

To say that this year’s March was a complete antithesis to 2012 would seem to be an understatement of the year.

The mean temperature figure of 37.1F (2.8 C) compares with 47.1 F (8.3 C) for the record warmth of March last year. This year’s mean daily maximum shows the extraordinary persistence of daytime coldness at 41.3F (5.1 C) which is 14.1F (7.3C) lower than 2012, which registered a record 55.4F (12.4C). Taking the long term review, last month was the fourth coldest March on my records, the previous ones being 1969 with 35.9F (2.2C ), 1962, 35.5F (1.9C ) and 1947, 35F (1.4 C).

Looking at the trend of March temperatures since the start of this century we have been favoured with eight warmer-than-average months, peaking with last year’s record, and also 44.4F (6.8 C ) in 2002 and 44.7F (7C) in 2003.

Coupled with several warm Marchs in the 1990s, the clamour of the climate change advocates suggesting that Britain’s spring seasons were three weeks to a month earlier than they used to be grew louder, alas, only to be knocked into oblivion by the weather’s punctuation marks in recent years!

Total rainfall figures for March were slightly above normal, 58.7mm (2.34in) compared with the long-term average of 37mm (1.5in). Since 2000, the driest Marchs have been 2003, 19.1mm (0.76in), 2009, 19.3mm (0.77in), 2011, 9.3mm (0.37in) and 2012, 17.3mm (0.69 in).

One interesting, if not remarkable, point is revealed in two 12-month rainfall comparisons. Firstly, the total rainfall for 12 months, April 1, 2011 – March31, 2012 amounted to 593.4mm (23.73in), compared with the successive period, April 1 - March 31, 2013, which has recorded almost double the amount, 1131.7mm (45.26in).

This comparison gives a considerable clue relating to the record warmth of March 2012. Coming in the wake of a lengthy dry spell, the dry soils and sunny days in 2012 encouraged the daily maximum temperatures to exceed 61F (16C ) on eight days through the month.

In the wake of the past 12 months’ high rainfalls, deficient sunshine and protracted winter cold, the year so far has produced a negligible springboard for an exceptionally late spring.

Looking at some of the main weather features last month, the opening days saw quiet, anticyclonic conditions as a high pressure system over Scotland slipped southwards. Overnight fogs and a few days with sunny glimpses saw daytime maxima of 48F (9 C) on March 2, and just one singular reading of 50F (10C ) on March 7. However, our fate was about to be sealed when a weak front over northern England on March 9 reversed its movement southwards with a simultaneous spread of continental Arctic air from Russia towards the British Isles.

Temperatures plummeted, with maxima 38F (3.5C ) on the 9th, and 32F (0C) 0n the 11th. Snow showers increased as the winds backed north-easterly, bringing snow around the northern promontory of the Cleveland Hills and down the Vale of York.

The reversal of frontal movement on the 9th was actually the precursor of identical developments on March 21-22 when a much more vigorous front moved northwards over England, then became quasi-stationary over northern England before moving southwards yet again.

Snowfalls associated with this front adopted the characteristics of what is termed “orographic snowfall”, accentuated precipitation caused by forced upward movement of snow-bearing winds on the eastern slopes of the higher Dales, such as Upper Uredale and Wensleydale.

The strong easterly flow became constricted through the higher hills and valleys, resulting in heavy, drifting snowfall, whereas the Vale of York experienced relative immunity from heavy snow, thanks to the snow-shadow effect in the leeward shelter of the North York Moors.

There are several underlying factors concerning the weather of March, not least the sunlessness, with 14 completely sunless days.

This was due to low pressure over France causing moisture in the upper atmosphere to encroach the Arctic air over England.

However, the benefit of this cloud blanket was the protection from severe night frosts, the sharpest being 23F (-5C) recorded on March 12, 14, and 29.

Overall, the principal controlling factor was the near record Greenland High, which attainted a pressure of 1957 millibars in the third week of the month, closely resembling the intensity of the same system in March 1962.

PROPSECTS FOR THE WEEK AHEAD

In a season like this one, the transition from wintry conditions to progressive warmth of spring is never straightforward, especially when what appear to be promising weather situations suddenly go pear-shaped! With the persistence of cold polar air to the north of the British Isles, a wintry backlash is developing, with low pressure centred over England, and a renewed flow of polar northerlies coming in behind. Rising pressure over the weekend should stabilise conditions into drier, brighter days – but not excitingly warm.

Unsettled, with periods of rain, sleet or snow, giving very wintry conditions over high ground into the weekend. Improving for next week, with drier, sunnier days and just a few showers, possibly still wintry over the hills. Temperatures still below seasonal normal, 45-50F (7 -10C) with overnight frosts returning, 32-28F (0 to -2C). North-easterly winds still prevelant.